Telephone trunking system.



PATENTED FEB. 12, 1907.

- W. W. DEAN.

TELEPHONE TRUNKING SYSTEM.

APPLICATION FILED JULY 19, 1902.

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UNITED PATENT OFFIOE.

I/ ILLIAM W. DEAN, OF CHICAGO, ILLINOIS, ASSIGNOR T O KELLOGG SWITCH- BOARD AND SUPPLY COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

r teeeione. reunions SYSTEM.

Specification of Letters Patent.

Patented Feb. 12, 1907.

To aZZ whom it may concern;

Be it known that I, WILLIAM W. DEAN, a citizen of tire United States of America, and resident of Chicago, county of Cook, and State of Illinois, have invented a certain new and useful Improvement in 'Iele phone Trunking Systems, of which the following is a speciiication.

My invention relates to improvements in telephone trunking systems adapted to interconnect subscribers lines terminating at different switcnb o ards It is often desirable wiiere communications between central otlices or different switchboards are infrequent, where the distances are great, or the expense of trunk-cir cuits is otlierwse excessive to employ trunkcircuits for establisi ing connections botli ways-tiiat is, for initiating connections at eitner end and completing tiiem at he other. Sucli trunk-circuits have been provided in connection with the so-called three-wire systems, in which systems the cut-oil relays for the lines are energized over local circuits extending tlirougliout tlie switckboard and independent oi' the talking-circuit and tlfi testing-terminals are connected with said local circuits; but they have not been pro vided with the usual apparatus employed in connection with trunk-circuits and do not operate in the usual manner. Sucli circuits therefore, altliougli desirable for some reasons, are objectionable on account of introducing apparatus not of standard type and for the further reason tlltt tire operation of establishing connections differs from that ordinarily employed.

One object of my invention is to provide a trunking system adapted for reciprocal operation, which is provided i n tlLC usual and standard apparatus, and wlt-icli operates in either direction in tire usual manner, wliereby the installation of tifiSG reciprocal circuits corresponds to the ordinary one-way-trunk circuit and the metiio d of or oration in establishing connections does not di'l'ler from tire usual one-way trunk.

A further obiect is to provide a trunk-circuit of tire kind described to operate in con nection with the Dunbar-1" or two-wire type of subscribers lines, the distinctive features in said lines being that the cut-oii relays are actuated over a portion of tlie talking-circuit and the testing-terminals are connected directly witli the talking-circuit, wliereby only two wires or cables extending tltrougliout tile switchboard are require d and only two cords are used in the operators connective circuits. With tliis type of line also but two-point connecting plugs and spring-j acks are require d.

Further objects are the provision of a simple and eilicienttrunking system adapted for reciprocal operation, in which special signaling devices are associated with each end of the trunk to properly attend and supervise the connections.

In carrying out my invention, wliicli has been worked out for commercial purposes, a trunkcircuit is provided with multipleswitcli connections at each end and also with a flexible cord and connecting-plug at each end. Provision is also made in connection with tiie multiple-switch sockets at each end, XVlLGIGbY wilen a connection is established at any one of the sockets the other sockets located at both ends of tie trunk have their electrical condition altered so as to be in condition to test busy. Moreover, when a connection is establisl cd at one of said sockets, as specified, tilG signaling apparatus associate d witn said end of tlie trunk is rendered inoperative, wliile tiiat at tle opposite end of ti e trunk remains in condition to operate in accordance with tile plan of tlie invention. Sucli signaling apparatus comprises a ringing-signal actuate d w .en ti e connecting-plug is inserted in tlie jack or switchsocket of a subscribers line \X'lliC-ll is rendercd inoperative upon tlie response of tie subscriber and is locked out during tl'ie remainder oi" tilG connection. 'I'ltere is also provided a second signal, wl icli actuates as a calling-signal wlien a connection lias been establisiicd at one end of tlie trunk to .attract the attention of tiie operator at tlie opposite end of ire trunk. A. disconnect-signal is also provided for said end of tlie trunk, whereby wi:.en a connection lLas been severed at tile initiating end the operator at tlie completing end-is notified. The usual cord-circuits are provided for tire operators at each switchboard.

'nvcniion nrtirer consists in tlie novel arr o enicnis and continaticns llereinaiter descnbed, and particularly pointed out in time appended claims, reference being bad to the accompanying drawing, forming a part of nected with the line L the trunk-plu g P.

this specification, in win ich the same reference characters designate like parts throughout, and in wlrici;

The figure represents a diagram of subscribel's lines tern' inating at different switchboards, the operators cord-circuits at each switchboard, and the trunk-circuit extending between the switchboards.

L and L indicate subscribers lines terzrinating at the sw itchboards E and F. The sub sciibei's lines are of the wellknown Dunbar or two-wire type, in which the cutoi'l relays are actuated over a portion ct the tells ing-circuit and the test g-ternpinals are also connected directly with. the talking-circuit. These lines are shown provided w ith a plurality ot subsciibei's stations, A and B being located on the line L, while C and D are con- As these lines are well known, further detailed description is not deemed necessary. Cord-circuits cooperating with these lines and shown at switchboards E and F are alike and are of the ordinary type used in connection with the twowire or Dunbar line-circuits.

H indicates the trunk-circuit, extending between the switchboards E and F, this circuit conipiising the line conductors 2 and 3,

extending between the multiple-switch connections or jacks J J located at the sw tchboard E, and the corresponding connec nterniinals J and J, placed at the switchboard F. It will be understood that as many of these jacks as is desi1 ed maybe employed at each switchboard, said jacks being lecat ed before the di'l'l'erent operators. Each jack is provided with pair of normally open contacts 4 and 5, which when the connectingplug is inserted in the jack are brought together by the lilting of contact 4 through. the medium of the tip-spring of the jack, and thereby conplete the switchboard E ii iii the sleeve side of the circuit the connection of the grounded cut-oil re y R and at the switchboard F the circuit oi the corresponding cut-oft relay R As the apparatus at each switchboard is Sill'illl, that located at one end only oi the trunk-circuit will be specifically described. TllGCUt-Ofli relay R is provided with armatures 6 and 7, which normally connect with conductors 8 and 9, tern .ina'iing in he windings "L0 and w of the repeating-coil W', a condenser 0 being interposed between said windings and a trunk-relay 1 being connected in parallel with said condenser. The opposite windings Z0 and 105 are conne ctcd with an interposed condenser 0 between the tip-sti nd i and the sleeve-strand s of the flexible cord, teririnating in the corresponding contacts of The forward portion of the tip-strand t is connected, through the normal contacts of the sleeve-relay T with high-resistance test-relay 1 to ground, seid test-relay serving when actuated to shortcircuit a portion of the operators telephonecircuit, whereby she is enabled to receive a busy signal, and s;id strand is conipleted through the iorward contacts of said sleeverelay when the latter is actuated, the sleeverelay being connected between the live pole of a battery B and the sleeve-strand 5- oi the trunk-cord. A tip-relay r is legged to ground from the tip-strand P. A ringingsignal S is provided for the trunk-cord, which is rendered inoperative and locked out by nieans oi the locking-relay r. A calling and disconnecting signal S serves to indicate a call iron]. the opposite end oi the trunk w on coiniection has been established therewith and to also give a disconnecting indication when the connection at the reverse end of the trunk has been severed. A suitable 1ingin.g-generatorg is provided in connect ion with the trunk-cord to enable the operator to cell through the nzedium of the usual selective key eiti r of the subscribers niounted upon a party-line or to call a single subscriber located on a line-circuit. The opposite end of the trunk-circuit is provided w ith sin ilar apparatus connected with the normal contacts oi the cut-off relay H a battery B serving to actuate the signals and relays thereat. The cord-cii cuit at board E is provided with plugs P and P and. the associated batteries B and B Slfl' ilar batteiies B and B being connected with the cord-circuit at th e sw it oh b oard F.

In the operation of the system, assuming that a subscriber on line L wishes to communicate with a subscriber on line L he lifts his receiver, thus permitting current from battery B to flow over the linc-circuit and operating the line-signal S of his line in the usual way. The operator noticing the signal inserts the answeringplug P of her cord-circuit in the answering-jack of the line, thereby completing a circuit from the battory B over the sleeve-strand of her cordand actuating the same to disconnect the line signaling device and to connect the switclirsockot with the limbs of the telephoneline. At the same time the supervisory relay 1 is actuated, and the cooperating relay 1* is likewise operated by current over the line-circuit, whereby the supervisory signal S is prevented from operation. Upon learning that a subscriber located on line L is wanted recourse is had to 13116 trunk-circuit H, the condition of which is tested by means of tlie connecting-plug P of the operators cord-circuit. If the line is idle, it is apparent that the test-rings of the jacks of the trunk-circuit are entirely free from any source of current, and inasmuch as the tip of the testing-plug is grounded through. the testrelay r no click will be received by the operator. Upcn finding the line idle the callingplug P is inserted in the jack of the trunk IIO before the operator, this act serving to lift the tip-spring of the trunk-jack to connect contact 4 with the contact 5, thereby connecting the cut-off relay R with the sleeve side of the trunk-circuit, over which a path for current from the battery B is completed over the sleeve side of the cord-circuit, 11 .8 operating the cutoff relay, and thereby disconnecting the conductors 8 and 9, leading to the flexible cord and plug connected with that end of the trunk. The apparatus associated with the flexible end of the trunk is therefore entirely disconnected through. the remainder of the connection, and all the parts associated therewith are rendered inoperative. At the same time the testing-rings at all the jacks, including those at the switchboard F, are placed in condition to test busy by current from the battery B associated with the cord-circuit at E. It will therefore be seen that had the trunk been in use at the time the operator touched the tip of her connecting-plug P to the testring of the jack before her a testing-circuit would have been completed. over the tipstrand of the cord-circuit and through the test-reh y r, which woulri have si rfit-circuited a portion of the operators talking-circuit to cause a click in her receiver. The insertion of the connecting-plug P serves also to operate the sleeve supervisory relay 1" in the cord-circuit at E, which disconnects the testrelay and completes th the cord-circuit for conversation. Simultaneously current flows to the opposite end of the trunk-circuit over conductor 3, the nor mal contacts of cut-off relay R conductor 9, and through the trunk-relay 1, w ich is high resistance, and back to the other pole of the battery 15 over the tip side of the trunkcircuit and the tip cord-strand. This trunkrelay r is of sufficient resistance to prevent the actuation of the supervisory relay r located in the cord-circuit, whereby 't-iIG supervisory signal 8, associated therewith, remains lighted. The actuation of the trunk relay 1 closes, through its forward csnacts, the circuit of the calling-signal S s circuit being traced from the live pole of the battery B over conductor 40, through the signal S", and over conductor 53 and armature 51 of the sleeve-relay r to ground. This lamp is therefore lighted, in response to which the operator depresses her key 7c" and connects her telephone with trunk-circuit to learn the number of the party wanted. 'Upon obtaining this information the subscribers line is tested by touching the tip of the trunk-plug 3 to the test-ring of the adiacent jack of the subscribers line. If the line is irile, no click will be received; but if in use the said test-rings are connected with battery, and a testingcircuit will be completed over the tip-strand of the trunk-cord and through the test-relay e tip talking-strand of listening- I but the Siltl signai by reason of lts second path being opened I l l l l i l L l 1 1", which will be actuated and will cause a click in the operators receiver. Upon findthe line idle the plus" P of the trunk-circuit is inserted in adjacent jack or switch socket of the line if, and the corresponding ringing-key 7r or is operated to ring the de sired subscriber. As the bells of the subscribers are logged. to ground from the different line conductors the keys 7c and k are correspondingly arranged to connect the generator 9 between ground and the proper line conductor, the key 7r, which connects the generator 9 with the tip-conductor, being adapted to complete a path from the battery 13' over conductor 47 and including resistance 66, through LLLO cut-off relay R" of the lino-circuit, to maintain the same operated durin ringing. The sleeverelay r is thus actuated by current from the battery B over the sleeve-strand of the trunk-cord and through the cut-off relay R of the line to ground. The actuation of this relay opens the circuit before traced of iLl'LO calling-signal S At the same time a cir nit is completed through the ringing-lamp S from the battery ever conductor 40,through the forward contact and sting 51 of sleeve-relay r, and thence over conductor 53, through the la 11p S1 and the normal contacts of the locking relay 1". T

ihis signal is therefore lighter and indicates to the operator that the called ubscriber not yet responded.

Upon the response of the calied subsori: er a lOW-lGSiStSJK e p ath for current from the b attery B is eompieted over the sleeve strand of the trunk-cord and the steeve-conductor of the subszrib ers iine through the low-resistance instruments at the suits" "hers station and cook over the tip-eondt etor of the line, the tip-strand of the cord-circuit, and through the relay 1* to ground. The latter reia therefore actuates and short-circuits the trunk-relay 1. The removal of the resistance of the trunk-relay r from thnietaliic circuit of the out 1 end of the trunk permits su'flir ient flow of turreit therein from rte f B" to operr e the tip supervisory in the A cord-circuit at the station E, as the eiiei t of retiri g the superviaiSand indict g to the A operator that t .e coiled suit, or has responded. The trunk-reia; armr ure now falls back, whirl completes anoth r circuit for the lamp S which new acts as a diseonne:ting-signal; is prevented from lighting through the spring 57 of the tip-reiay r. .l his spring 57 oi the ilD-TOlA-f, 1' serves to untiaily complete, throu h its forward contact,

the circuit of the tearing-relay 1*, which 1 causes the same to operate by current from the b atter f' B and to not oniy cut out the rmmeg-famp 8*, thus ioaiing to the B operator that the call ed subsf or has responded, but also to complete a locking-circuit f0 itself through its grounded armature, which circuit can only be broken by the denergization of the sleeve-relay 1"". In case of crossing of the plug-contacts during the process of making the connection, and thus actuating the locking-relay 1", the lockin -oircuit is opened by the ringing-keys 7c and 7P, so that as soon as the ringing operation has terminated the ringing-lamp Sr is lighted. Under these conditions the subscribers are in communication, the battery B furnishing current to the line L for talking, the battery serving to actuate the supervisory signals and relay associated with the cord-cir 'auit and the cut-oil relay of the trunk, as well as to alter the eleotrioal condition of the testrings of the trunk-jacks, while the battery 13 furnishes current to the called line for conversational purposes and for the operation of the various relays and signals associated with the incoming end'of the trunk.

At the termination of the conversation when the subscriber upon the line L returns his receiver to its hook the supervisory signal S is operated in the usual manner. When the called subs? iber hangs up his receiver, current is cut oil from the tip-relay r at the end ofthe trunk at which the connection r as completed, thus opening the short circuit about the trunk-relay r and completing through its spring 51 a p ath for current through the dis oonneotlamp S The trunkrelay, however, is immediately actuated to open the circuit of Slitl lamp, while the resistanee of the trunk-relay is so great as to prevent the continued operation of the supervisory relayr. The supervisory signal S associated therewith is therefore operated to indicate to the initiating operator that the conversation has terminated. This operator nowtalres down the conneoti on, whiah results in deenergizing the trunk-relay r at the opp osite end of the trunk, thereby comp eting the circuit of the disconne t-lamp from the live pole of the battery B over conductor 40 to spring 51 of the sleeve-relay r, and thence over conductor 53 through the lamp S, the armature and back contact of the trunk-relay, and the back contact and spring 57 of the tiprelay r to ground. This signal is therefore actuated, and then the operator at this end of the trunk withdraws the trunk-plug from the called-suhsoribers line and restores all parts to normal condition.

It willbe apparent that order or instructi on circuits may be employed between the operators, if preferred; but the above operation is the one most commonly used with this arrangements of trunks.

In case a subscriber at exchange F wishes to communicate with a subsorib er at the exchange E the connection at the oilice F is completed by means of the cord-shoult shown by inserting the answering-plug P in the jack of the calling-line and after ascertaining the order by inserting the plug P in one of the jacks J or J of the trunk-circuit H. The insertion of the cord-circuit plug into the jack of the trunk results, as described with reference to the connection at the opposite end of the trunk, in actuating the cut-oil relay R which disconnects the plug P at that end of the trunk and its associated apparatus. The desired connection is then completed by the operator at the opposite end of the trunk, who tests the condition of the called line by means of the plug P of the trunk, and if the line is idle inserts the said plug into the jack of the wanted subscriber. The same operation of the ringing-signal, calling-signal, and disconnect-signal takes place with reference to this end of the trunk as des oriloed with reference to the former end, wherebythe answer of the called subscriber and the replacement oi his telephone upon its hook actuates the supervisory signal associated with the connecting end of the cord-circuit at the switchboard F.

In case the call at either of the switchboards had been for a subscriber whose line terminated at said switchboard the connection would have been completed directly through the cord-circuit by means of the connecting-plug P thereof.

It will be understood that when a line is found busy the operator may communicate directly with "he in'oiating operator or with the waiting subscriber, or an ordinary busyback and dent answer signal-chcuit may be provided in connection with the i d plugs of the trunk, whereby when ,l esoonding condition of a callejl line .0 trunk-pl maybe inserted in the arliacent j ck of sai signaling apparatus thereby fy the initiating operator and tl to waiting subscriber.

The ground connecti ns .hereinbefore refe .ii to at each of the diilj'erent switchbeads, will be understood, may and in practice l usually are one and the same, or y may be the common ol'lice return, alit is found by experience that it is practically necessary to place a dead ground upon one sizje of the common battery. It is also ap ai3ent that the other poles of the batbe grounded, so far as the operthe system is concerned, the only necessary being to remove the ound connections, replace them by ucte s, and place the ground-conn the eppcsit e pole of the battery. 0 exact dimensions of the relays ...e essence of my invention, I have .s-zecured good results from trunl -relays of lifteon-t?iousand-ohms resistance, tip and sleeve relays of one-hundre:l-chms resistance and lcckn relays of five hundred ohms, while the oth parts may be of the usual or desirable dimensions. it is also apparent so far as some features of the invention are siasri concerned that the lines may terminate in single cords and plugs in place of the double 2 cores shown and described. and that the;

trunks may tern'iinato in jacks and plugs in place ol' the plugs and co;

and suostitu' still come n no not, therefore, wish to be confined in all IOSPOCL'S to the particular construction and t1ittl""6lll0ili1 here shown and described. Any nested. arrangement of the trunks may be had, the plugs terminating at a section by themselves, the jacks in separate banks, or any other pyefor erl arrangement. It is also understood that ie tes t-relays are preferably connnon plugs at each operatons position.

in an application filed June 28, 1902,

Serial he. 113,581, I have shown and specifically dGSTilJCQl a one-way trunking system including linccircuits cooperating there with of type herein described, as well as a busy-back and dont circuit and apparatus. 1 do not intend hoJein to claim the subject-matter of the said application; but

What 1 do claim as my invention, and desire to secure by Letters Patent, is-

1. he combination with a nk-oirouit extending between multiple switchboards, adapted for reciprocal operation, and provided with in iple-switch connections at each swi" card; of testing-tcrininals for said 017' nccticns connected with the talkingcircuitduring cenveisat' n, and nieans when connection is establisl' Ii at any of said switch connections for plac said testing-tenninals .0 other oi said switch connections in condioicn to test busy, substantially as described.

2. The combination with a ti ink-circuit exteri .n between multiple swltc -boards, adapted for r ciprecal c eraticn, and pro- 4 multiple-s2 ns at each switchboard; of testing-terminals for said connections ccnnctell with one side the telling-circuit i ng conversation, and an operas rs cennec g-circuit for establishing connection with. one of said switch connections, and means when said ccnnecthe said test- 1' switch con tic-n is established for placin 1ngternnnals at all ct "he 0 nee-trons 111 con ition to test busy, substantially as descifbed.

3. The combination with a trunk-circuit extending between multiple switehboards, adapted for reciprocal operation, and provided with multiple-switch connections at each switchboard; of testing-twainals said connections connected with one side of the talking conversation, an

irctit dtrr operators cor rooting-c 1t tor establishing connection with one of said switch connections, and a source of current associated with said connecting-circuit and adapted to be Other ways of 1 out my invention and other changes 1 answer signaling.

I connected with the trunk talking-circuit l when said connection is established, whereby said testing-terminals at all of the other switch l connections have their electrical condition altered and are placed in condition to test busy, substantially as described. l a. The conib'nation with a trunk-circuit 1 extending between multiple switchboards, l adapted for reciprocal operation, and prol vided with multiple-switch connections at each switchboard; oi testing-terminals for i said connections, and nleans aetu ated wholly at any one of said switch connections for l placing the testing-terminals at all of the l other switch connections in condition to test l busyduring conversation, substantially as 1, described. l 5. The combination with a trunk-circmt lextending between multiple switchboards, l adapted for reciprocal operation, and provided with multiple-switch connections at each switchboard; of testing-terminals for each of said connections, a cord-circuit adapted to be connected with said connections, and a source of current associated with said cordcircuit, and means for altering the potential of all of the testing-terminals of said switch connections from said source when the said cord-circuit is connected with any of the switch connections, substantially as described. 6. The combination with a trunk-circuit extending between multiple switchboards, adapted for reciprocal operation, and provided with multiple-switch connections at each switchboard; of testing-terminals for said connections connected directly with one side oi'- the talking-circuit during conversation, a cord-circuit adapted to be connected with any of said switch connections, a source of current associated with the cord-circuit and adapted to be connected with the trunkcircnit when a connection is established there with by said cord-circuit, signaling apparatus connected with the cord-circuit and adapted to be operated by said source of current, l said source of current also serving to vary the potential of said testing-terminals at both ends of the trunk to place them in condition to test busy, substantially as described.

7. The conibination with a trunk-circuit extending between dii'lerent switchboard-secl tions and having a switch-socket and a flexible cord terninating in a connecting-plug at each end of the "1 ink to adapt the same for reciprocal operation in interconnecting telephone-line circuits for conversation, of operaters connective circuits at each end of the rank to establish connections with said sockets, the said connections bein conpleted by rneans of the inconing cords and plugs at the opposite end of the trunk, substantially as described. 8. The combination with a trunk-circuit 1 extending between di'll'erent switchboard-sections and having multiple-switch sockets in the form of spring-j acks and a flexible cord ternunatlng in a connecting-plug at each end of the trunk to adapt it for reciprocal operation 1n interconnecting telephone-line circuits for conversation, of operators connective circuits at each of said switch-sockets to establish connections therewith, said connections being conpleted at the opposite end of the trunk through the niedium of the flexible cord and connecting-plug, substantially as described.

9. The combination with a trunk-circuit extending between diflerent switchboard-sectlons and having multiple-switch sockets and a flexible cord terminating in a connectingplug at each end of the trunk-circuit to adapt the same for reciprocal operation in intercoiinectlng telephone-line circuits for conversation, of operators connective circuits at each end of the trunk to initiate connections between the callinglines and said sockets, an i connections being conpleted at the opposite ends of the trunk by connecting the trunkcord with the called-subscribe1"s line, and rrieans actuated when connection is establlshed at one of said switch connections for placing the other switch connections of tlte trunk in condition to test busy, substantially as described. i

10. The combination with a trunk-circuit extending between different switchboardsections and having a multiple number of switch-sockets and a flexible cord terminatlng in a connecting-plug at each end of the trunkc1rcuit to adapt the same for reciprocal operation in interconnecting telephonc ine circuits for conversation, of operator's connective circuits at each end of the trunk to initiateconnectionsbetween the callinglines and said sockets, said connections being completed at the opposite ends of the trunk by connecting the trunk-cord with the calledsubscribers line, and means actuated whollv at the section where the connection is estalil shed for placing all of the switch connections in both ends of the trunk in condition to test busy during conversation, substantially as described.

11. T he combination with a-trunl. -circuit extending between the ditto rent switchboardsections and having a plurality of switchsockets and a flexible cord terminating in a connecting-plug at each end of the trunk- 0112011) to adapt the same for reciprocal operat on in interconnecting telephone-line circuits, of means for establishing connection from the calling telephone-line at either switchboard with the proper switch-socket of the trunk in initiating the connection, said connection being completed at the other end of the trunk by connecting the trunk-plug at said end with the called line, substantially as described.

12. The combination with a trunk-circuit extending between different switchboard-- sections and having a flexible cord terminating in a connecting-plug and a switch-socket in the term of a spring-jack at each end to adapt the trunk-circuit for reciprocal operation in interconnecting telephone-line circuits for conversation of operators connective circuits at each end of the trunk to establish connections with the said sockets, signal ing apparatus at each end of the trunk, and means actuated when connection is established with one end of the trunk for disconnecting the apparatus associated with said end, substantially as described.

13. The combination with a trunlecircuit extending between difl'erent switchboardsections and having a flexible cord terminating in a connoctingplug and a switch-socket in the form of a spring-jack at each end to adapt the trunk-circuit for reciprocal operation in interconnecting telephone-line circuits for conversation, of operators connective circuits at each end of the trunk to establish connections with the said sockets, signaling apparatus at each end of the trunk, and means actuated when a connection is established with one end of the trunk for disconnecting the apparatus associated with said end, and for actuating the said apparatus at the opposite end of the trunk, substantially as described.

1.4. The combination with a trunk-circuit extending between different switchboardsrctions and having a flexible cord terminating in a connecting-plug and a switch-socket in the form of a spring-jack at each end to adapt the trunk-circuit for reciprocal operation in interconnecting telephone-line circuits for conversation, of operators connective circuits at each end of the trunk to establish connections with the said sockets, signaling apparatus at each end of the trunk, and means when a connection is establishc d with one end of the trunk for disconnecting the apparatus and plug associated with said end, substantially as described.

15. 'l he combination with a trunk-circuit extending between multiple-switchboard sections adapted for reciprocal operation and provided with a switch connection at each switchboard, a disconnect-signal at each end of the trunk normallyconnected therewith, and means when connection is established with one end of the trunk for disconnecting the said signal at said end, substantially as described.

16. The combination with a trunk-circuit extending between switchboard sections adapted for reciprocal operation and pro vided with a plug and switch at each switchboard, disconnect signal at eachend of the trunk, and means when a connection is est ablishe d at one end for disconnecting the signal and the plug at said end of the trunk, substantially as described.

17. The combination with a trnn i-circuit extending between swit-chboard-sections and having a flexible cord terminating in a connecting-plug, and a switclvsocket in the form of a spring-jack, at each end to adapt the trtnk i'or reciprocal operation in interconnecting telephone-line circuits for conversation; of operators connective circ s at each end to establish connections wi h said sockets, and a cut-oil relay for ea h end of the trunk actuated when a connection is established at said end to cut oil the associated trunk-ping, substantially as described.

1S. he combination with a trtnx-circr extending between multiple switehboards and provided with a switch connection at each switchboard, of operators connective circuits at each end oi the tirnk to establish connections with said connection, a ent-otl' relay for each end of the trunk actuated over a portion oi the talking-circuit when connection is established with said end to cut oil the remaining portion of the trunk at said end, substantially as described.

19. The combination with a trunk-circuit extending between ditlerent swit chboard-sections and having a flexible cord terminating in a connection-plug, signa ng; apparatrs, and a switch-socket in the form of a springjack at each end oi the trcnk to adapt the trunk for reciprocal operation in interconnecting telephone-line circuits lor conversation; of operators connective circrits at each end to establish. connections with the sockets, a cut-off relay for each end the trunk actuated over a portion 0'? the talkingcircnit at said end when connection is established with any 01' the associated sockets to cut oil' the corresponding ph and signaling apparatrs, substantially as described.

20. The combination with a tri'nk-cir "sit extending between multiple switchboards adapted for reciprocal operation and provided w h switch connections at each switchboard, of a signaling apparatits at each end of the trunk, a cut-off relay at each end normally disconnected therefrom, and means when connection established at one end to connect said cut-oil relay with the trunk-t ircnit and to operate the same over a portion the talking-circuit, said normal disconnection preventing the operation of the other cut-oil relay by the current impressed upon the trunk-line, sub stantially as desc i 21. The combination with a trrnk- I extending; between di'tlerent switehboard-sections and having a switchocket at one end and a flexible cord and connecting-pkg at the other, of a signal at the end having switch-socket to adapt the t1 FDli-Cilfil'iib for reciprocal operation, a cut-oil relay associated with said socket, means for operating said relay when connection is esta i lied with said socket to render the said signal inoperative, and a supervisory relay at SLl( l 1 l i socket end adapted to operate in series with said cat-ct. a when a connection is established at said end, snbstanti as described,

The combin h a triink-c nit extendingbet een di witchbcard-sections, 01' a s. one end and a s t :h-socket at 'llexible cord and connecting-plug at the i, a callim it the end of the trunk i re sochet is located and havcontrolled by current from d o the tr; k whereby the asap-ted I *"ccal operation, a cut-oil relay associated i i h the said socket and adapted to be operated by en ent flowing or a portion of the tall n t-ci ,it when connection is established w h said socket, said relay sei ing; to render said signal inoperative, substantia as described.

23. The com inalion with a trrnk-circuit extending between di'llerent switehboard-sections, of a switch-socket at one end of the trunk-circuit and flexible cord terminating in a connecting-plea at the other end, a calling-signal at the socket end of the trrnk having its op "ation controlled by the other end of the ti-onk whereby tl ink is adapted i reciprocal operation, a catch relay associated v. ith the said socket biit normally disconnected "from the trunk, means when connection is established with the said socket to connect the coil 0'? said cat-oil relay with one side of the talking-circrlt ol the trunk and to operate the same, said latter relay serving when operated to rennet said signal inoperative and a siipervisory relay at said socket end adapted to operate in series with said cnt-oli" relay when a connection is established at said end, snbstan 1y as described.

24:. The combination with a trunk-circuit extending between dilierent switchboard sections and havi' a flexible cord terniinating in a connecting-plug and multiple-switch coi'inections at each end to adapt the trunk circuit for reciprocal oper ion for interconnecting telephone ine circuits for conversation; of a calling-signal for each end of the trunk, and ireans when a connection is es -tablished with the switch-socket at either end to render inoperative the signal at said end, and to act: te the signal at the other end, substantially as l scribed.

25. The conibina on with a trunk-circuit extending between diflerent switchboardat or end a flexible cord iatmg in a connect plrg' and in-ultiple-switeh oonnecti the trunk-circrit reciprocal operation meeting telephone-line circuits for ;'-signal for each end clay ior each end of for inter-cor conversation, c1 a call i of the k, a cut-ct the trrink-circiiit adapted to be actuated over a crtion of the talking-circrit when connection is established with the switchscckets, said relay serving to render the calling-signal at the same end of the trunk inopns at each end to adapt erative, and means for actuating the callingsignal at the other end of the trunk-circuit as soon as the connection is established, substantially as described.

26. The combination with a trunk-circuit extending between diilerent switchboardsections and having a flexible cord terminating in a connecting-plug and llldltlPlB-F circuit for reciprocal operation for interconnecting telephone-line circuits for conversa- 131011, or a calling-signal lor each end oi the "toll connections at each end to adapt the trunktrunk, a cut-oil relay at each end of the v trunk-circuit normally disconnected there- 1 from, means for connecting said relay with one side of the trunk-circuit and actuati: it by current thereover when connection is established with one of the switch-sockets, said relay serving to render the signal at the same end inoperative, while the signal at the other end is operated upon the establishing of the said connection, substantially as dey scribed.

27. The combination with a trunk-circuit extending between different switchboards adapted for reciprocal operation, and prcvided with multiple-switch connections at each switchboard of a ringing-signal at each end of the trunk to indicate the response of the called subscriber at the end employed. as l the incoming end, and means for rendering inoperative the similar signal at the other and outgoing end of the trunk, substantially as described.

28. The combination with a trunl :circuit extending between different switchboards, adapted for reciprocal operation and provided with multiple-switch connections at each switchboard; a ringing-signal at each end of the trunk to indicate the response of the called subscriber at the end employed as an incoming end of the trunk, means for rendering inoperative the similar signal at the other and outgoing end of the trunk, and means for looking out the first signal at the incoming end during the remainder of the connection, substantially as described.

29. The combination with a trunk-circuit extending between dillerent svitchbcards, adapted for reciprocal operation in connecting subscribers lines for conversation, and provided with multiple-switch connections at each switchboard; of a rii'lging-signal at each end of the trunk to indicate the response of the called subscriber at the end 5 employed as an incoming end, a disconi'iectsignal at each end of the trunk to indicate at the incoming end when the connection has been severed at the end employed as the outgoing end of the trunk, and means for rendering the corresponding signals inoperative at the outgoing end when connection is established at said end of the trunk, substantially as described.

30. The combination with a trunk-circuit extending between different switchboardsections, adapted for reciprocal operation, and provided with multiple-switch connections at each switchboard of a ringing-signal at each end of the trui'ik to indicate the response of the called subscriber when the end is employed as an incoming end, a disconnect-signal at each end of the trunk to indicate at the said incoming end when connection has been severed at the corresponding outgoing end oi the trunk, means for looking out said ringing-signal at the incoming end after the subscriber has responded, and means for renderin the corresponding signals inoperative at the outgoing end when connection is established with the trunk, substantially as described.

The combinauon with a trunk-circuit between oiil'erent sw-tchboards a.. apte-l for reciprocal op eration and provices. with both switch connections and plugs at each switchboard; of a signal at each end of the trunk, means for eisconnectnig the signal at the outgoin end of the trunk when connechon is establshed with said end in iintia tag a connectlon, the si nal at the other en 1 of tire trunk being actuated. at such time to indicate a call, said latter sgnal also serving a tisconnect-signal when the conversation has terminated and the connection with the trunk has been severe i at the initiating enyl, substantially as described.

32. The combination with a trunk-circuit extending between different switchboards and having multiple-switch sockets and a connecting-dug at each end to acapt a circuit for reci rocal operation, a socket at one end and a plug at the other bein employed in each connection for conversation, of means associate. with each plug to in ate when a connection has been establishes. w.th a socket *oslte end and at the close of the at the conversation, when the connection has been ing ein' zloyol in each connectlon for conven s 11, me 1 s associate l with each plug to in .cate w on a connection has been establlsheil with a socket at the opposite end of the trunk, the sa"' sockets at both of said on s being place: 1 con illliOil to test busy when the connection has been established at one of said sockets, and means for disconnecting the plug and associated apparatus at ITO and at the close of the'conversation when the connection has been severed at said socket, a ringing-signal associated'with each plug to 34. A trunk-circuit extending between difindicate the response of the called subscriber ferent switchboards and having multiplewith which the plug is connected, said ringswitch sockets and a connecting-plug at each ing-signal being prevented from again operend to adapt the circuit for reciprocal opera- I ating after the response of the called subtion, a socket at one end and a plug at the l scriber during he existence of the connecother being employed in each connection for tion, means associated with each plug for se conversation of means associated with each lectively calling the subscribers upon a partyplug to indicate when a connection has been l line, and further means for disconnecting the established at a socket at the opposite end of plug and its associated apparatus at the same the trunk and, at the close of the conversaend as the socket employed for the connection, when the connection has been severed tion, said disconnection taking place when at said end means associated with each plug the connection is established therewith, subto indicate the response of the called subl stantially as described. scriber when the'plug is employed in making 36. The combination with a trunk-line terthe connection, and means for disconnecting minating at each end in both jacks and plugs, the plug and associated apparatus at the opl of cord-circuits adapted to be connected with posite end of the trunk when connection is I said trunk at either end, and subscribers established with the corresponding socket, l lines at either end with which said trunk is substantially as described. adapted to connect, suitable signals for said 35. The combination with a trunk-circuit trunk, and means whereby said signals will extending between different switchboardbe suitably actuated when said trunk is used sections having multiple-switch sockets and 1 in either direction, substantially as described. a connecting-plug at each end to adapt the 1 Signed by me at Chicago, county of Cook, circuit for reciprocal operation, a socket at State of Illinois, this 17th day of July, 1902.

one end and a plug at the other being employed in each connection for conversation, l WILLIA M DEAN of a signal associated with each plug to indicate when a connection has been established E wlth a socket at the opposite end of the trunk the said socket end of the trunk when the connection is established, substantially as described.

Witnesses:

ROBERT LEWIS AMEs, GAZELLE BEDER. 

